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Synchronization

Clocks must be kept synchronized if a timestamp mechanism is to be used. A simple and easy to implement clock synchronization algorithm is the one that goes by the name Cristian's algorithm.

The server must also act as time server [52] under the assumption that server time is correct time or for the fact that it is important that the clients are synchronized with the server (even if it is out-of-sync with real time). Of course, the algorithm will only work properly if the client does not change media (causing the messages to and from the server to have a large gap in communication time) during synchronization.

Figure 3.2: Cristian's algorithm (running on the client)

An explanation of the different "times" used in the above algorithm can be found in Table 3.1. These will also be used in later chapters.

Table 3.1: Times

$T$	real Time
$T_{C}$	Client Time
$T_{S}$	Server Time
$T \! S$	Time Skew	$T \! S$=$T_{S}$-$T_{C}$

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